Mining method for working large-scale mineral deposits by the caving system

ABSTRACT

The mining method of this invention is particularly suitable for the underground extraction of large mineral deposits, wherein a subsidiary road is formed perpendicularly to the work face from which the mineral deposit is to be removed. A boundary subsidiary road is formed substantially perpendicularly to the subsidiary road, a first mine tunnel is formed by removing the mineral deposit from the work face along the subsidiary road until the boundary gate road is reached. Then the material around said first mine tunnel is collapsed to fill the same along the subsidiary road and the collapsed matter is consolidated along the subsidiary road. Finally a second mine tunnel is formed along the subsidiary road. The second mine tunnel can be horizontally or vertically adjacent to the first mine tunnel.

BACKGROUND

The invention concerns a mining method, especially for the recovery ofuseful minerals such as coal, bauxite, etc., from large-mineraldeposits, utilizing a caving system of high output, increasedconcentration of production, and increased safety.

A general requirement of increasing importance in mining is maximisingthe purity and concentration of the mineral and its output. Thus, miningat reduced production costs without leading to a deterioration of therecovery conditions such as of labour safety and reliability ofoperation are important goals.

These goals come increasingly into force in the recovery of usefulminerals occurring in large deposits in several sections lyingside-by-side and/or in several layers. Among such minerals is coal,which is of ever greater importance as an energy carrier.

Large mineral deposits make mass production of great concentrationpossible. However, in the long term this result can be attained for themost complete possible extraction, that is total working, of the mineraldeposits only where the yield of the individual sections and layers isobtained by a modern and suitable mining method, for example mechanicalcaving and block caving with favourable mining and working conditionsand increased safety being guaranteed throughout.

Multi-step exploitation of large-scale mineral deposits conventionallyis achieved by leaving behind safety pillars in widths of 100 m or more.The minerals are left in the deposit and then, if necessary, are minedout later or are abandoned in place. This is a particularly prevalentmethod where the work areas or sections lie side-by-side. On the onehand, these pillars have the task of securing or at least improving themechanical conditions of working. On the other hand, especially in thecase of combustible minerals, the pillars play an important part in themutual isolation between the individual working areas and sections, aswell as in effecting a ventilation seal, whereby the danger andoccurrence of endogenous mine fires are considerably reduced.

However, an undoubted disadvantage of mining effected with safetypillars is that the usable mineral in the safety pillar can subsequentlyonly be recovered, if at all, under substantially more difficultconditions and at appreciably greater expense. Where mining takes placein several layers, the mineral cannot safely be recovered. The foregoingnot only signifies a great loss of mineral resources, but also is sooneror later detrimental to the conditions of mining the other parts of themineral deposit.

These conditions arise in all mining methods, i.e., room-and-pillarworking, strip working, longwall working, long face working with complexmachinery, and also in the case where the usable mineral is won byfull-bore (blasting) work; at best, especially in the latter case, thetechnological and winning disadvantages are less important.

A method is known, for example according to Soviet Pat. No. 589,401, inwhich an artificial pillar is formed. It is characteristic of thismethod that it is suitable for exploitation in two layers in the casewhere a stone band lies between the two seams. The two seams or layersare to be selected so that the stone layer lies between them. The upperlayer is extracted by winning in long strips, the roof is secured byanchoring and then a longwall gallery is driven, from which anartificial pillar is formed up to the top of the deposit. Then the lowerlayer is won and thereupon an overhead cave-in extending to both layersis initiated.

However, the range of utility of this method is limited. The individualtechnological steps do not render continuous winning possible and in allcases reduce the working output. The method is also costly, sinceinterim securing operations (anchorings) are required which areexpensive and complicated in execution and also make the winning moredifficult.

An aim of the invention is the development of a method of mining inwhich the disadvantages of the known methods are eliminated or reducedand which can be used in a wide range for all mineral deposits,especially for mineral deposits of great extent. The present methodseeks to enable the recovery to be advantageously cleaner (purer usablemineral), and the production to be more concentrated, less expensive andof increased yield, labour safety and operational reliability.

SUMMARY

In the method according to the invention this mineral deposit is dividedup as necessary, horizontally and/or vertically, into sections and/orlayers, along these and along the presence of the mineral depositsecondary roadways and, if desired, boundary roadways (openings) aredriven, and the mineral is recovered by the caving system. It ischaracteristic of this method that at least on one side of the secondaryand boundary roadways and/or at the top of the layer or layers followingthe first layer, a consolidated or strengthened zone is formed in amanner known per se. Expediently the zone is formed by consolidation ofbroken mineral and possibly by pillars of broken material (hereafter:breakage) or mineral material. The mineral material is recovered byworking in an advancing and/or retreating system in one or more sectionsand/or layers in a manner known per se. The secondary and/or boundaryroadways or the individual sections thereof are broken off and abandonedafter the mineral material is recovered Conveying the recovered mimeraland ventiliation of the mine are carried out through the open secondaryand boundary roadway sections and it is possible to do this through thegallery.

According to a preferred embodiment of the method, one secondary roadwayis driven open before the working face, while another is drivenfollowing the working face.

According to a further preferred embodiment, the boundary roadway isdriven open only on one side, in the direction of the width of themineral deposit.

A plurality of consolidated caved zones can be established on a longwallface. For the formation of the consolidated zones, waste material fromthe longwall face can be used as an additive. This waste material can beutilized better if the maximum particle size is kept below 1 mm,suitably 0.4 mm-0.6 mm.

Preferably CO₂ gas is employed for the consolidation of the breakage.The consolidated zones are formed up to the roof of the subsidiary road.

In a likewise advantageous manner of performing the method, of thisinvention, the mineral deposit or seam is recovered in divided layersand/or in layers with block caving.

Preferably, the working of the mine is carried out alternately individed layers and in block caving; it is advantageous if the firstlayer is exploited by block caving.

An embodiment is wherein the working of the individual sections iscarried out alternately by advancing and retreating working. It isadvantageous if in the first section the mineral deposit is recovered byworking in an advancing system.

According to a further advantageous embodiment, the section of thepreviously driven secondary or subsidiary gallery following the workingface is abandoned by caving.

Finally, in another preferred embodiment the secondary roadway drivenopen following the working face is used as conveyor roadway.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in greater detail by reference topreferred embodiments diagrammatically illustrated in the accompanyingdrawings, wherein:

FIG. 1 shows a mineral deposit (slice) divisible into several sections,in plan view, with alternating forward and reverse (advancing andretreating) working, with a consolidated zone without mineral pillars,and with boundary roadways;

FIG. 2 illustrates the embodiment according to FIG. 1 in plan view, withexclusively advancing working sections;

FIG. 3 is a sectional view taken along the plane indicated by linesIII--III in FIG. 2;

FIG. 4 shows the forward working of a single section with theconsolidated zones lying beside the subsidiary galleries within thesection, in plan view;

FIG. 5 is a section taken along the plane indicated by lines V--V inFIG. 4;

FIG. 6 shows a three-slice working of the seam, in section, where thefirst slice is a divided slice; and

FIG. 7 is a sectional view of working of a thicker seam which can beworked in several slices, where the first slice is excavated with blockcaving.

Explanation of the various types of lines:

The solid lines designate the seam boundaries, the active (open)secondary and boundary roadway sections, the consolidated zone and theworking face; the longer broken lines relate to the secondary andboundary roadways which have been broken down (caved); and the dotted(or shorter broken) lines indicate the further section-slice boundariesand the division of the seam.

Explanation of the numerical designations from 10 to 89:

The first digit of every two-digit number is always the serial number ofthe section or slice. Of the second digits:

0=section;

1=left-hand side subsidiary gallery (secondary roadway) of a givensection, as seen in the Figures;

2=the consolidated zone of the corresponding section;

5=slice of a beam divided into working slices;

6=slice with working by block caving;

7=the consolidated zone of the roof of the corresponding layer or slice.

Other numerical designations:

90=boundary roadway

95=roof.

DETAILED DESCRIPTION

Working (mining) in a section 10 according to FIG. 1 is carried out inan advancing system in the course of which secondary (subsidiary)roadways 11, 21 are driven together with the working face. As workingprogresses the parts lying behind the place of working are (gallery)caved in (light cross hatching) and in the course of this, along theroadway 21 within the section 10 a consolidated zone (heavier crosshatching) is obtained by breakage consolidation. After the working ofthe section 10 the winning machine is shifted through the boundaryroadway 90 into the section 20 and the working is continued in aretreating or reverse system. In the course of this, at the same time asthe formation of the working, that section of the secondary roadway 31which lies behind the working face is also formed, as well as theconsolidated zone 32 extending beside the roadway 31 by caving-in behindthe gallery. Furthermore the part of the roadway 21 is caved between theworking face and the boundary roadway 90. Transport and ventilation takeplace through the open part of the roadway 21, the work face, the openparts of the roadway 31, this is the secondary transporting roadway),the boundary roadway 90, also by way of the trunk transporting andventilation roadways (not shown).

FIGS. 2 and 3 show the working, taking place in several sections, of asimilar seam in which the working of every section is forward oradvancing working. This working method can be advantageous in theworking of rising coal seams, especially under watery conditions. (Thisworking method can naturally also be performed in a retreating system ofworking.) In both cases advantageously the subsidiary conveyor roadwayshould be a roadway section that is established together with the workface, that is to say, is a roadway section still in a good condition.The disadvantage is that the face equipment has to be transported alonga long distance on reinstallation. In a longwall face section 60according to FIGS. 4 and 5, consolidated ribs or `tacks` are formedbetween subsidiary roadways 61, 71 in the waste on each side. The roofis left in a naturally caved state between these consolidated `tacks`,as on the rest of the face.

The working of the mineral seam according to FIG. 6 is carried out inthree layers or slices. The slice (formed by dividing the seam intoslices) below the roof 95 is excavated and broken down (caved in). Atthe foot of the breakage, a consolidated zone 27 is formed by breakageconsolidation, which can expediently be effected in the conventionalmanner by the supply of CO₂ gas to serve as the roof of the slice 26.The load-bearing capacity of this zone is arranged such that it delaysthe breaking in of the roof of the next succeeding slice 26 securely forthe requisite time. Thus the usable mineral of the layer 26 can beextracted by block caving, so that a relatively clean recovery can berealised with minimal working loss. The consolidated zone of appropriateload-bearing capacity to be formed on the floor of the slice 26 makes itpossible to work the next succeeding slice 35, formed as a dividedslice, under a consolidated roof.

In FIG. 7 there is illustrated the extraction in accordance with theinvention of a very thick mineral seam which therefore can be worked insubstantially more slices than in the above case. In this case the firstslice 16 is extracted by sublevel caving (shrinkage). The caved waste isconsolidated to form the roof of the slice below 27. The next slice 25is taken by conventional methods and the caving is again consolidated37, to form the roof of the next slice 36, which is again extracted bysublevel caving.

Of the advantages connected with the method in accordance with theinvention the following should be emphasized especially:

(1) The method can be used in mining by a caving system of all mineralsirrespective of the extent of the mineral seam, and offers an especiallyadvantageous recovery method in the working of large or very largemineral deposits.

(2) The consolidated zones make it possible to isolate the broken ores(which may be inflammable) of the individual sections and layers fromone another and from the usable mineral deposits not yet involved in themining. At the same time the consolidated zones--that is, those playingan active part in the taking up of the pressure--have the effect that alower pressure acts upon the subsidiary and/or boundary roadways, whichoffers significant advantages in the dimensioning, securing andmaintenance of the roadways. In the case of multi-slice working thesecuring of the roofs of the individual slices by consolidated zonesenables one to use safer, cleaner methods involving less loss(shrinkage).

(3) With regard both to the economy of the resources of the earth and tothe desirability of continuous and safe extraction, it is of very greatimportance that the formation and use of consolidated zones permits asubstantial reduction of size, and furthermore, in many cases theelimination, of the otherwise necessary separating pillars.

(4) An additional advantage involved with the consolidated zonesconsists in that more favourable conditions of rock mechanics (pressurewave repulsion or deflection) are brought about by their use in thesubsidiary roadways and also in the gallery.

(5) A sequence of the mining of the successive sections and/or layerscan be developed which is optimally adapted to the particular nature ofthe mineral, the dimensions and arrangement of the mineral seam and thegeological circumstances.

(6) Additionally, it is possible to design and carry out continuously aproduction system of great concentration and capacity, without incurringa rise in costs and without detriment to safety. On the contrary, afundamental feature of the method consists in a more modern and saferextraction with lower production and operating costs.

Further pertinent essential elements are:

Substantially fewer preparatory roadways have to be driven open andmaintained; the time required for readjusting, assembling anddismantling the mining and conveying equipment is reduced; as a resultof the shorter open roadway length less mechanical equipment isnecessary for the conveying of the materials and minerals; more modernventilation can be ensured.

We claim:
 1. A mining method for the underground extraction of largemineral deposits, comprising:(a) forming a subsidiary roadperpendicularly to the work face from which the mineral deposit is to beremoved; (b) forming a boundary road substantially perpendicular to saidsubsidiary road; (c) forming a first mine tunnel by removing the mineraldeposit from said work face, along said subsidiary road until saidboundary road; (d) collapsing the material around said first mine tunnelto fill the same along said subsidiary road; (e) consolidating thecollapsed matter along said subsidiary road; and (f) forming a secondmine tunnel along said subsidiary road.
 2. The mining method of claim 1,wherein said second mine tunnel is substantially horizontally orsubstantially vertically disposed relative to said first mine tunnel. 3.The process of claim 2, wherein the mineral is extracted by descendingslices.
 4. The method of claim 1, wherein waste material from the workface is used as an additive for the consolidation of the caving.
 5. Theprocess of claim 4, wherein the waste material used for theconsolidation is previously ground to a particle size of less than 1 mm.6. The method of claim 4, wherein the waste material used for theconsolidation is previously ground to a particle size of from 0.5 mm to0.6 mm.
 7. The method of claim 1, wherein the mineral is extracted bysublevel caving.